One of the common complaints regarding Microsoft is that the company has problems eating its own dog food. Even though it promoted Windows Presentation Foundation as the programming framework for building Windows and web applications, it so far failed to produce any significant WPF applications itself. None of Microsoft's major applications use WPF (Expression Design and Blend aren't major), which does not help in promoting it as the Next Big Thing. This may all change in the near future, as a small but extremely popular Microsoft application is about to make the switch to Windows Presentation Foundation: MSN Windows Live Messenger.